# US 5,350,231 A · Double worm extruder with meshing screws

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- Number: US 5,350,231 A
- Document ID: US5350231A
- Status: Granted
- Kind: A
- Application number: 08/143,826
- Filed: 1993-10-27
- Granted: 1994-09-27
- Earliest claimed: 1992-10-29
- Assignees: Friedrich Theysohn GmbH
- Inventors: Horst Eigruber
- Web page: https://patentgrep.com/patent/US5350231A

## CPC

- B29C 48/41: Intermeshing counter-rotating screws
- B29B 7/489: {Screws (B29B7/482 takes precedence)}
- B29C 48/60: Thread tops
- B29C 48/03: characterised by the shape of the extruded material at extrusion
- B29C 48/402: {the screws having intermeshing parts}
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS

## Abstract

A double worm extruder has the ribs of its screws of trapezoidal cross section between divergent flanks to minimize wear of the housing surface.

## Claims

### Claim 1

A double-worm extruder, comprising:
an elongated worm housing having a pair of adjacent laterally overlapping bores extending longitudinally in said housing and defining an open figure-eight cross section therein; and
a respective screw received in each of said bores, said screws being journalled in said housing and having longitudinally extending bodies formed with helical ribs projecting therefrom, the ribs of the screws meshing with one another, said ribs each being of trapezoidal cross section between outwardly diverging flanks.

### Claim 2 (depends on 1)

The double-worm extruder defined in claim 1 wherein said flanks include angles .alpha. with radial planes of the respective screw of at most 5.degree..

### Claim 3 (depends on 2)

The double-worm extruder defined in claim 2 wherein said angle .alpha. is at least 0.5.degree..